For centuries, it was known that people who survived smallpox became immune to it. For that reason, nearly every culture tried to induce immunity in healthy individuals. The Chinese used tubes to insert powdered smallpox scabs into their nostrils. In Turkey, pus from lesions was scratched into the skin.
Climate graph San Francisco. The driest month is July. There is 1 mm of precipitation in July. Most precipitation falls in January, with an average of 115 mm. Temperature graph San Francisco. With an average of 17.6 Â°C, September is the warmest month. In January, the average temperature is 10.4 Â°C. It is the lowest average temperature of the whole year. San Francisco Climate table // historical Weather data
Every day in San Francisco normally warms to over 40 Â°F (4 Â°C), and most reach 50 Â°F (10 Â°C). The city averages just 2 days a year when the thermometer reaches into the 90s Â°F (over 32 Â°C). The temperature normally doesn't climb above 100 Â°F (38 Â°C), even on the hottest days.